A new helcionelloid mollusc from the Cambrian of Greenland and Idaho (Laurentia)

Abstract

Ressericonella gen. nov., a new genus of helcionelloid mollusc, characterized by a narrow shell with a shallowly convex dorsal surface and flat to shallowly concave lateral areas, is described from the Cambrian of Greenland and Idaho. The type species is Helcionella aequa Resser, 1939 from the Langston Formation (Naomi Peak Limestone Member) of early middle Cambrian age (Miaolingian Series, Wuliuan Stage, Albertella Biozone). Ressericonella pipalukae gen. et sp. nov. occurs in the latest early Cambrian (Cambrian Series 2, Stage 4, Bonnia？Pagetides elegans Biozone) of southern Freuchen Land, North Greenland. Silicified specimens of Ressericonella pipalukae from North Greenland preserve two-layered shell structure in which an inner layer with a transverse fibrous pattern similar to lamello-fibrillar structure is overlain by an outer layer with fine threads radiating from the apex.